- Like ancient Egyptian architectural materials
- that were recycled in the construction of ancient Greek Alexandria,
- so ancient Greek materials from the construction of that city were reused in subsequent centuries by Roman, Muslim, and modern builders.
The sentence presents a similarity. Ancient Egyptian architectural materials were recycled in the construction of ancient Greek Alexandria. Similarly, ancient Greek materials from the construction of the same city were reused by others in subsequent centuries.
The problem with the sentence is that it seems to mix two constructions that are used to present similarity i.e. "like X, Y" (X and Y are nouns) and "Just as M, so N" (M and N are clauses). The given sentence begins with "Like"; however, the main clause begins with "so". If "like" were to be used, we would need the clause to begin with the subject "ancient Greek materials" and not "so".
Since "so" is used in the non-underlined part, we need to change the underlined part so that it uses "Just as" construction.